This invention relates to an electrical box support constructed of telescoping struts having means to releasably lock the struts and at an outer end of each strut a studengaging tab that can be bent to conform to different box depths.
The terms xe2x80x9cboxxe2x80x9d and xe2x80x9celectrical boxxe2x80x9d as used herein are intended to refer to a junction box, receptacle box, switch box, terminal box, connector box or the like as are known in the electrical trade. The teachings of the patents described below are given for background and are deemed to be incorporated herein by reference.
U.S. Pat. No. 1,506,330 issued in 1924 recognized the need for an electrical box support capable of accommodating an electrical box of a known depth and studs of different spacing. The ""330 patent teaches the practice of forming an electrical box support from a pair of telescoping, channel formed struts, each having a face to which the box could be attached. The ""330 patent also teaches bending the ends of the support to form right angled tabs for mounting the box support to and between adjacent studs. The ""330 patent box support however required that adjustments for boxes of different depths be made by locating the bent ends of the box support at different locations on the sides of the studs.
U.S. Pat. No. 1,789,124 issued in 1931 also recognized the need for adjusting the length of an electrical box support by bending the ends of the support to accommodate to studs of different spacing.
U.S. Pat. No. 2,233,334 issued in 1941 also recognized the need for an electrical box support capable of accommodating electrical boxes of different depth and mounting to studs of different spacing. The ""334 patent teaches the practice of forming an electrical box support from a single bar having a face to which the box could be attached. The ""334 patent also teaches bending the ends of the support to form right angled tabs for mounting the box support between and to adjacent studs. The electrical box support of the ""334 patent however was not adjustable lengthwise and also required that adjustments for boxes of different depths be made by locating the bent ends of the box support at different locations on the sides of the studs.
U.S. Pat. No. 2,788,188 issued in 1957 illustrates in one embodiment an electrical box support constructed of a pair of struts which telescope within each other so as to be able to adjust to different spacings between the studs and providing a face to which the box could be attached. In the mentioned embodiment, the ""188 patent also illustrates the practice of prebending the ends of the telescoping struts to form tabs useful for attaching the box support to and between adjacent studs. In another embodiment, the ""188 patent illustrates an electrical box support formed from a single flat sheet with bendable tabs at each end each having a plurality of grooved, embossed or etched lines at different locations along which each tab can be bent in the field to form a flange at right angles to the plane of the sheet. Thus, the ""188 patent can also be construed to teach the practice of being able to form an electrical box support either with prebent tabs or with flat tabs adapted to be bent in the field.
With regard to the practice of providing lines of weakened metal, bend points, a line of holes or the like in an electrical box support, to facilitate bending or breaking of the metal along a particular line, reference is also made to U.S. Pat. No. 4,399,922, issued in 1983, for an electrical outlet box support. The ""922 patent illustrates a pair of weakening lines used to facilitate bending of a portion of the support; U.S. Pat. No. 4,483,453, issued in 1984, also illustrates an electrical box support in which a plurality of parallel lines of holes are used to facilitate breaking of excess metal; and U.S. Pat. No. 4,673,235, issued in 1987, also describes an electrical receptacle subplate having two pairs of such bend lines.
U.S. Pat. No. 1,800,813, issued in 1931, illustrates use of a lengthwise V-groove in the strut of an electrical box support and of a series of preformed holes to facilitate insertion of nails, screws or the like. U.S. Pat. No. 4,967,990, issued in 1990, recognizes use of pilot holes to facilitate the starting and use of metal screws for securing the box to a face on one of the telescoping struts. The electrical box support described in the ""990 patent comprises a pair of telescoping struts adapted to be mounted between two spaced-apart wall studs. Each strut comprises an elongate web of sheet metal forming a front face of the strut, a pair of side walls extending rearwardly from the side edges of the web, and a channel formed inwardly of the web running substantially the full length of the web between the side edges of the web. Inwardly turned flanges connect to the side walls and define the bottom of the channel. Pilot holes are spaced along the web at relatively closely spaced and regular intervals whereby an electrical box may be attached to the strut in a selected position lengthwise of the strut by placing the back wall of the box flush against the front face of the web over the channel and then fastening the box to the strut by using screws threaded through selected pilot holes.
Applicant""s prior U.S. Pat. No. 5,405,111, issued in 1995 for a Bracket For Anchoring Apparatus Between Wall Studs, also illustrates a feature of interest to the present invention, namely, the use and advantage of detents. As disclosed in the ""111 patent, detents are used rather than holes to facilitate installation of self drilling sheet metal screws for attaching apparatus to the bracket. So far as applicant is aware, the ""111 patent is the only known prior art reference which illustrates the use and advantage of detents in an electrical box support though it has been known to use a series of holes to facilitate insertion of nails, screws and the like as seen for example in the aforementioned U.S. Pat. No. 1,800,813, issued in 1931 and U.S. Pat. No. 4,967,990, issued in 1990.
With the above as background, it is to be noted that use of the telescoping type electrical box support has introduced a problem in that the known struts which telescope one within the another often come loose before being installed because of the typical free-sliding fit between the telescoping struts of the support. Thus, if an installer, for example, is on a ladder and is in the process of installing a telescoping type electrical box support of conventional construction, the typical telescoping struts particularly when held vertically because of their relatively loose sliding fit are apt to separate and permit one of the struts to fall, thus risking harm to both people and objects below.
With regard to the need for establishing a relatively tight fit between struts of a telescoping type electrical box support, U.S. Pat. No. 2,788,188, issued in 1957 describes a telescoping type electrical box support but specifically refers to the sections of the support being xe2x80x9crelatively slidable.xe2x80x9d U.S. Pat. No. 2,809,002, issued in 1957, refers to the relation between two struts forming a telescoping type electrical box support as permitting xe2x80x9crelatively free-sliding movement.xe2x80x9d U.S. Pat. No. 5,386,959, issued in 1995, describes a telescoping type electrical box support in which mention is made of the two sections of the support xe2x80x9cnot being readily separablexe2x80x9d. The ""959 patent however does not show nor do any of the other mentioned patents show, any kind of releasable locking mechanism which would permit telescoping struts once assembled to be held vertically without separating and yet be readily adjustable lengthwise by manual pressure applied to the struts. In dealing with this same problem, B-Line Systems, Inc. has recently started marketing a telescoping type electrical box support formed with inner and outer sections and with pilot holes in each section such as shown in B-Line""s Patent 5,209,444, issued in 1993, and a resilient finger (not shown in the ""444 patent) formed intermediate the length of the outer section and having a protrusion which resiliently engages and slides on an opposite surface of the inner section apparently for the purpose of reducing any tendency of one section to slide on the other. However, the sections are never releasably locked as with the present invention.
The term xe2x80x9cstudxe2x80x9d as used herein is intended to include structural members in a building surface, including wall studs, joists, rafters, etc. The term xe2x80x9cwallxe2x80x9d as used herein is intended to include ceiling surfaces as well as vertical walls.
Therefore, the object of the invention is to provide a further improved telescoping type electrical box support which accommodates and can be field bent to accommodate boxes of different depths, can be adjusted to different stud spacings, and, of particular importance to the invention can while being installed, maintain a relatively tight but releasably locked engagement between the telescoping struts. Other objects will become apparent as the description proceeds.
The improved electrical box support of the invention comprises in a first embodiment at least two and in a second embodiment three struts that are assembled in telescoping relation to accommodate different stud spacings and also having means to accommodate different depths of electrical boxes. The box support assembly of the invention is formed of outer and inner struts with a series of interengaging detents, i.e. conical or hemispherical shaped depressions, so that the struts can be moved to relative positions in which the outer strut detents engage and nest into opposed inner strut detents to releasably lock the struts comprising the two-strut assembly together at some selected length. The outer strut can be manually moved relative to the inner strut to temporarily disengage the detents and change the releasably locked length of the box support assembly. One end of the outer strut and an opposed end of the inner strut are formed with a tab that is adapted to be bent for mounting to adjacent building studs at a depth appropriate to accommodate an electrical box to be mounted thereto.